Variable time delay electronic apparatus



Dec. 14, 1948.

D. E. SUNSTEIN VARIABLE TIME DELAY ELECTRONIC APPARATUS Filed Sept. 20, 1944 I i mi ENTo'R; 24ml? fax/2.1M

Patented Dec. 14, 1948 VARIABLE. TIME DELAY ELECTRONIC APPARATUS. David' E .SunsteimtElkins Park, Pa., assignor to Philco. Corporation; Philadelphia; vl='a., a. corporationrofi lennsylvania Application'september.20, 1944, .Serial No. 554,962

3-.Glaiims; 1 The present invention relates to space dis charge apparatus; and concerns particularly apparatus of the type-in which an" electric'emission beam or electronicbeam is produced:

An' object ofthe invention is to'provid'e" improved methods and apparatus for" producing' Still another object is. to provide a..compact,.

readily operated modulator for. producing frequency modulation or phase modulation by means. of a. relatively wealemodul'ating signal.

A. further. object is to provide an ultrahigh.

frequency oscillator which may be modulated;

Still another object. is. to. provide arrange.-

ments for utilization. or. for. control of. transit.

time. effects...

Other and furtherobjects .and. advantages. will.- become apparent as. the description. proceeds.

Incarrying out the inventioninone ofQthe .pre-

ferred embodiments thereof,. a discharge, tubev is. provided of the. type having. meansfor. forming. a.-

beam of electrons which may bein the formof. a sheetlying along a.plane,.a.cone or.- other. configuration of. such. a. nature. thatelectrons. may

be deflected so.. as to. bend..thebeam. onsheet of;

electronsinto a distorted shape. A,.suitable col,

lector. plate is. provided. which. has. .considerable.

lengthin the direction of emission. of the. electrons in the beam so that by deflectionuofifthe.

beam or. distortion. of: the. shape... thereof, the

pointat... which. the electrons impinge. upon the. collector plate. may be. varied. Accordingly, timedelay. efiects may be.produced as. a. result ofelectron transit. time. Asignal .impressedon the electronbeam maybe variably delayed ,by means; at a second signaLor. modulating. signaLarr-anged.

to bend or: distort-the beamor sheet of. electrons Avbetter. understanding of. theinvention will beeafforded by the. following. detailed description 2 which may be produced 1 in" asigna-l supp the apparatus of Fig; 1; and

Fig. 3 is a schematic and" circuit diagram of arr embodiment of the invention. in which an' eleclied to tron beam is varied inuvelocit'y instead of; being bent or distorted.

Like reference characters are utilized through out the drawing. to: designate" like parts.

The apparatus illustrated iniFig: 1 comprises avacuum tube ll, having aconventionalindi: rectly heated cathode I I2;. a. conventional intensity control electrode or'grid13, meansxforformr ing the electrons emitted from: the cathode- I2; into a beam orsheet andanaanode orrcollectorz 5 Thebeamtforming*meansxmaytake the form as illustrated inFig: 1 of a pair ofbeam'rforming. electrodes or plates |4 .shown.as grounded; hav-' ing a slit or aperturelibetween them through which a stream oftelectrons It; may be emitted and focused if a flatsheet'formof. beam'a's d'ee-i' sired. It will be understood; however, thatifra; funneli-shapedbeami is desired: ora disc-shaped beam consistingiof a plurality *of radially extending rays, the-:form and: relative positionsof: theelectrodes l2, l3 and 'lll maybeyariedf accord-' ingly.

Preferably, a screen grid; lenselement, or fo'-- cusing anode- I1 is also provided havingmeans: such as a source of'"direct current I8 for maim taining the focusing anode I Tat a potential above the cathode l2, whichifor convenience" is shown as" grounded: The electrode I1. insures also that electrons which have passed? through it travel with a'velo'city substantially independent of the potential. on electrode I3..

If a flat sheet form of beam such asxillustrated' as I6 is employed; the collector or anode may take the form of a longitudinally extending plate i9; It will be understood; however, that thecollector- |9.-.'Wi]1.b providediwith a suitable form in relation to. the other; electrodes enumerated according to the shape: of beam desired;

For distortingrthe beam f6, or' in the. case: of:

a-pencili-shaped beam or a .ribbon-form beam; simply bending it fromra normal central position in the tube; 1 I, suitable defleotingpla'tes such as a pair. of electrostaticplates-:21 and-v 22 ofthe; type employed in cathode ray indicators and;

oscilloscopes are provided: The deflection plates 2|: and 22 will, ofcourse. take a suitablestead of electrostatic may also:be--employed;. or

if. simplified construction .is desired; deflecting;

voltage may be applied between the electrodes l4, omitting the plates 2|a22.

A source of anode voltage 23 is provided for energizing the collector anode |9, and in order to enable a signal to be taken from the apparatus, a load impedance 24 may be connected in series between the collector |9 and the anode voltage supply 23. A pair of conductors 25 and 26 may be connected to the ends of the impedance 24 for connection to a load 21 or other signal receiving means. r

If a signal such as a rectangular voltage pulse. for example such as illustrated by the wave 28 of Fig. 2 is applied to the intensity control grid I 3, a similar signal having substantially the same shape but delayed as represented by the wave 29 will appear at the output terminal conductors 25 and 26 as the result of the transit time effect,

that is to say the time required for the electrons.

to travel from the emitting cathode l2 to a point 3| at which thebeam .IB impinges onethe collector IS. The point at which-the beam Hi impinges upon the collector l9 may be varied by varying the voltage applied to the beam deflecting means, in this case the deflection plates 2| and 22. By varying the voltage applied to the beam deflecting means, the time delay between the signals. 29 and 28 ofFig. 2 may be varied.

I Improved operation, particularly with respect to reducing the defocusing effect of the collector Ill-upon the electron sheet or beam- IB, may be obtained by providing a second:long plate-form anode 32 in a complementary position with respect to the collector-anode Hi. In the particular form of tube illustrated, the anodes I9 and 32 areiboth flat plane anodes substantially parallel lying on opposite sides off the center axis of'the tube along which the beam l6 would.

normally travel if undefiected by the deflecting means 2 l22. .The anode 32 may be held at the same average potential as the anode l9 so that preferably a source of potential difference such as abattery 33 is provided for maintaining the potential of the anode 32 below that of the powersupply for the collector-anode Hi.

If desired, a reversable arrangment may be provided in which signals of reversable polarity may be applied to the beam deflecting means 2|22, in which case the'beamlfi may be deflected toward either of the anodes l9 and 32 according to the polarity of the beam deflecting voltage or signal. If the anode 32 is connected to the conductor 26 instead of to the conductor 25, signal output of a given polarity may be obtained for beam deflecting'signal input of either polarity. i

If desired, the anode 32 may be composed of a material forming a good emitter of secondary electrons. In this case, an increased output may be taken from the anode IS, the normal collectoranode. The latter arrangement will be found to Where the construction of the anodes is suchas to roduce either a flat sheet 16 of. electrons duced by beam deflecting means such as the plates 2| and 22 acting to distort the shape of the sheet of electrons, that is changing the angle of the cone or disc of electron emission so as to 'vary the distance between the cathode l2 and the point 3| at which the electrons impinge upon the collector-anode l9.

The arrangement may be utilized for modulation of a radio frequency signal especially an ultra high frequency radio signal where very rapid variations in polarity and in modulation are required.

For example if the voltagewave form of an exciter 34 is to be modulated by a source of modulating voltage 35, the exciter 34 may be coupled to the intensity control grid l3 of the tube H, and the modulating voltage source 35 may be coupled to the beam deflecting means, in this case the deflection plates 2| and 22. The load 21 may take the form of antenna or a power amplifier or the like for utilizing the frequency or phase modulated signal. It will be understoodv age source 35 may becoupled to the second anode 32, the plates 2| and 22 being ornitted.

To illustrate the latter connection, double throw switches 36 and 31 are. shown having switch blades 38 and 39 respectively shown in positions for closing the circuits .producing the arrangement previously described where the plates 2| and 22 are utilized for modulating. If the modulation is to be accomplished or the time delay efiect is to be produced by means of the anode 32, the switch blades 38 and 39 are thrown to positions opposite from those shown, whereby the modulating voltage source 35 is disconnected from the plates 2|-22 and connected to the anode 32, which is under this circumstance disconnected from the tie-in with the collector anode |9.

The arrangement may be utilized as a simple amplifier for ultra high frequency service or as an ultra high frequency oscillator. For producing an ultra high frequency generator or oscillator, theload circuit may be coupled to one of the control circuits, for example the intensity control grid l3 or the deflection plates 2|22. For the sake of illustration a feed-back link coupling or tickler coil 4| may be provided having a primary winding 42 in series with the load 21 or if desired in series with the load impedance 24 and having a secondary winding 43 adapted to be connected in series with a control circuit' A double throw switch 44 is shown to illustrate conversion of the apparatus illustrated inFig; '1

from a carrier modulator in which the'wave of the exciter 34 is modulated by the source 35 to a self oscillatory high frequency generator; The switch 44 is illustrated as comprising a movable blade 35 coupled to the intensity control grid It, a stationary terminal 46 coupled to the exciter 34 and a second stationary terminal 41 to the winding 43 of the feed-back device 4|. -Other means for feed-back coupling may, of-course, be employed. If thei'blade 45 is moved from the position contacting the terminal 46 to the position contacting the terminal 41, the output of the collector anode, [9 will ,be fed back tothe intensity control grid 13 to produce oscillation.

If amplitude modulation is desired instead of left in the positions illustrated in the drawing may be appreciated from a concrete example of various specific dimensions and electrical values. It Will be understood, however, that the invention is not limited to specific values or relationships between them, and that the following Values are given merely for the sake of illustration. If the length of the anodes l9 and 32 is chosen as five inches, and if 500 volts are applied to the screen grid 11, then at an output frequency or a carrier frequency of megacycles, 360 degrees of phase modulation may be obtained, while at a carrier frequency of 2500 megacycles 36,000 degrees of phase modulation may be obtained.

Even greater phase modulation or deviation L may be obtained, if desired, by means of an alternative embodiment in which the velocity of the electron stream is controlled instead of the point of impingement of the stream and anode as illustrated in the arrangement of Fig. 3.

Referring to Fig. 1, it is apparent that by virtue of the input applied to the intensity control grid l3 and by virtue of the fact that electrons leaving the deflecting means 21-42 are traveling at constant velocity substantially independent of the amplitude of the input signal at the intensity control grid !3, the point 3| at which the beam [5 strikes the anode i9 is determined primarily by the intensity of the signal applied by the modulating voltage source 35. Since the target I9 is in the form of a long plate, the distance along the plate l9 which the beam 16 travels before striking can be varied considerably by the variation of the potential of the modulating voltage source 35. In this manner the transit time between a wave supplied by the exciter 34 and an output Wave taken from the terminals 25 and 26 is varied.

A similar result may be achieved by employing a fixed point of pickup or collection of the electrons in the beam 16, and providing means for varying the velocity of the electron stream. In this case the deflection-producing means 2l2t may be omitted and the anode collector or target i9 is changed in shape and position so as to lie across the path of the beam It. The apparatus illustrated in Fig. 3 may have electrodes l2, l3 and H similar to and corresponding to the electrodes shown in Fig. 1. However, the beam forming plates l4 and the beam deflecting means 2 l- -22 are omitted as well as the complementary anode 32; The collector w anode is changed in form and position as represented at l3 in Fig. 3 so as -tolie substantially'normal to the direction of the beam or ribbon of electrons Hi. "As in the case of the "apparatus 'of Fig. 1, the conformation of electrodes may also be such as to'utilize a sheet of electrons of funnel shape, or to utilize a radially extending electron sheet requiring a concentric arrangement of electrodes where a greater power output is desired than may be available from a pencil beam or a ribbon of electrons.

For varying the velocity of i the stream of electrons H3 in the region between electrodes I 1 and IS, a velocity changing electrode la-may be provided, and in order to prevent changes in current at the anode l9 resulting from changes in modulating voltage applied to the electrode 48, a counteracting electrode 99 may be provided which is mounted relatively close to the screen grid or lens element l l. Preferably the velocity controlling electrode 58 is'mounted relatively closeto the anode IS in order to exert a maximum effect on the transit time of electrons. The-counter.- acting electrode 59 is preferably supplied with a potential of suitable magnitude I86 degrees out of phase with the potential applied to the velocity controlling electrode 48. The delaying signal or modulating signal from the source may be applied in push-pull, preferably unbalanced between the electrodes 48 and 49. For example, a coupling transformer 5| may be provided having a primary winding 52 with terminals 35' for connection to the delaying or modulating voltage source 35 and having a secondary winding 53 connected between the electrodes 48 and 49 with a tap 54 thereon, preferably connected to a source of negative voltage such as a C battery 55 to provide sufficient bias for preventing the electrodes 48 and 49 from drawing current. The other connections may be similar to those employed in the apparatus of Fig. 1. For example, intensity control grid terminals 34 may be provided for connection to a carrier or exciter source 34 and the output may be taken from across the load impedance 24' by means of conductors connected to the ends of the resistor 24, or if desired one of the output conductors may be directly grounded as represented by the conductor 25' in Fig. 3.

The electrodes 48 and 49 may be in grid form or may be constructed as meshes of radially extending strips or rods similar to the velocity control grids provided for the catcher and buncher cavities of ultra high frequency tubes of the Klystrom type, for example.

The amount of delay of the input signal from the terminals 34 or the phase modulation which may be obtained for a given input voltage at the terminals 35' depends upon the length of the drift distance D between the velocity control electrodes 48 and 49.

Certain embodiments of the invention and certain methods of operation embraced therein have been shown and particularly described for the purpose of explaining the principle of operation of the invention, and showing its application, but it will be obvious to those skilled in the art that many modifications and variations are possible, and it is intended therefore to cover all such modifications and variations as fall within the scope of the invention, which is defined in the appended claims. 

